Metricbeat consists of modules and metricsets. A Metricbeat module is typically
named after the service the metrics are fetched from, such as redis,
mysql, and so on. Each module can contain multiple metricsets. A metricset represents
multiple metrics that are normally retrieved with one request from the remote
system. For example, the Redis info metricset retrieves info that you get when you
run the Redis INFO command, and the MySQL status metricset retrieves
info that you get when you issue the MySQL SHOW GLOBAL STATUS query.

To guarantee the best user experience, it’s important to us that only high quality
modules are part of Metricbeat. The modules and metricsets that are contributed
must meet the following requirements:

Complete fields.yml file to generate docs and Elasticsearch templates

Documentation files

Integration tests

80% test coverage (unit, integration, and system tests combined)

Metricbeat allows you to build a wide variety of modules and metricsets on top of it.
For a module to be accepted, it should focus on fetching service metrics
directly from the service itself and not via a third-party tool. The goal is to
have as few movable parts as possible and for Metricbeat to run as close as
possible to the service that it needs to monitor.